It is important to not only remove negative items from your credit report, but to add, new, positive lines of credit as well. Here are two easy ways to add credit to your report without adding undue debt:
Rent reporting: if you are currently renting, you can have your monthly rent payments show up as positive credit on your credit report. But be certain you make your payments on time, as late payments will also be reported.
Secured credit cards: unlike prepaid credit cards, with a secured credit card you get a credit line and your payment activity is reported to all the major credit reporting agencies. You deposit funds into the bank as collateral for the card. You can use the card like any other credit card, and rebuild your credit score by making the on-time monthly payments. Just make sure you keep your balances low, relative to the credit limit on the card.